This invention relates generally to ball-and-socket joints (hereinafter referred to as ball joints) and more particularly to a ball joint with a rubber-cushioned ball for improving the vibration and impact absorbing performance of the ball joint, which is suitable for use in mechanisms such as automotive suspensions and steering linkages.
Rubber-cushioed ball studs for improving the vibration and impact absorbing capability of ball joints are known in the prior art. In a known ball joint of this character, a layer of rubber is interposed between the ball-shaped extremity or head of the shank of the ball stud and a spherical outer shell. Examples of such structure are disclosed in the specifications of U.S. Pat. No. 4,334,795 to P. Westphal and Japanese Patent Application Laid-Open (Kokai) No. 1815/1982. As will be described more fully hereinafter, the rubber layer and the spherical shell encompassing the ball-head extremity of the ball stud in such a ball joint are substantially concentric relative to the ball-head extremity and are of substantially symmetrical shape above and below the equatorial plane passing centrally through the ball-head extremity of the ball stud perpendicularly to the axis of the ball stud.
In a ball joint having a known rubber-cushioned ball stud of this character, a load applied to the shank of the ball stud relative to the ball shell causes a great relative displacement in the stud axial direction between the shell and the ball-head extremity of the ball stud. Particularly in the case where the shank becomes displaced toward its extremity relative to the socket, if the shank is swung laterally about the ball center, the shank will tend to strike the rim of the socket opening and become damaged.
Still another problem accompanying this known ball joint is that when a great load acts on the shank in the direction toward its extremity, the rim of the outer or lower opening of the ball shell tends to bite into the lower or outer bearing of the socket in contact with the shell, whereby the bearing surface becomes damaged.
For these reasons, the use of these known rubber-cushioned ball joints has been restricted to those for low loads, or, for the same loads, a ball joint of this character was unavoidably of considerably greater outer diameter than a ball joint without a rubber layer.
Further, as noted hereinbefore, when these known ball joints with a rubber-cushioned ball stud are subjected to a load between the socket and the ball stud, the relative positional relationship between the ball shell and the ball-shaped extremity or head of the shank of the ball stud is disturbed, and the semispherical part of the rubber layer receiving the load becomes thinner. This tendency increases with increase in the applied load and gives rise to a disadvantageous lessening of the capacity of the rubber layer to absorb vibration and impact. In order to overcome this difficulty, it is necessary to increase the outer diameter of the ball-like extremity of the shank of the ball stud, whereby the size of the entire ball joint becomes disadvantageously large.